This is a (hopefully) complete list of the anti-tank guns used by the Wehrmacht, compiled by Antonio Pena with additional info from the other members of the forum.

German Weapons
2.8 cm schwere Panzerbuchse 41 (The first tapered bore gun used by the Wehrmacht)
2.8 cm schwere Panzerbuchse 41 auf leichterfeldlafette 41 (Same gun as above on special lightweight carriage for use by airborne troops)
3.7 cm PAK 36 (The standard AT gun of the Wehrmacht at the outbreak of War, and one of the best until 1941.)
3.7 cm Pak auf leichter Feldlafette (Same gun as above with lightweight carriage for airborne use)
4.2 cm leichter PanzerabwehrKanone 41 (The second tapered bore gun issued to the Wehrmacht in 1941. As for the sPzB41, production ceased in 1942 due to shortage of tungsten for his special ammunition)
5.0 cm PAK 38 (Developed from 1937, and issued to the troops in April 1940, also used in many selfpropelled carriages)
5.0 cm PAK 2.06/835 (Development started by Skoda in 1940 only a protype produced)
6.6 cm PAK 5/800 (Developed also by Skoda, only one proptotype produced)
7.5 cm PAK 40 (Development started in 1939, entered service in late 1941, basically a scaled up PAK 38, remained as standard AT gun until the end of war)
7.5 cm PAK 41 (The largest tapered-bore gun, some 150 completed. Same fate of the sPzB 41 and the lePAK 41)
7.5 cm PAK 6/860 (Enlarged version of the 6.6 cm PAK 5/800, only one built)
7.5 cm PAK 50 (Shortened PAK 40 on PAK 38 carriage, limited number issued to Infantry units)
7.5 cm PAK 44 (Experimental gun designed with two parts barrel)
8.0 cm Panzerabwehrwerfer 600 (High/low pressure gun, a Rheinmetall new ballistic idea, only 260 made)
8.0 cm Panzerwurfkanone 8H63 (The same gun as above with designation changed after troop trials)
8.1 cm Panzerabwehrwerfer L/105 (Prototype only, data unknown)
8.8 cm PAK 43 (Developed from Gerät 42, to become a useful AT Gun, with many unusual features as the vertical sliding block, the two sections barrel and the cruciform platform)
8.8 cm PAK 43/41 (A emergency solution due to shortage of carriages for the PAK 43, the last barrel married with the carriage of the FH 18 and the sFH 18 wheels, too heavy, loved for his punch and hated for the difficulties to move)
10.0 cm Panzerabwehrwerfer 600 (Experimental Krupp high/low pressure gun, several prototypes build)
10.0 cm Panzerwurfkanone 10H64 (New name for the above gun)
12.8 cm PAK 44 (Designed as dual purpose AT and field gun, probably the best AT gun ever produced)

Captured Weapons
2.5 cm PAK 112 (f) (ex-french M-34, the satandard AT gun of the French Army at the outbreak of the war)
2.5 cm PAK 113 (f) (ex-french M-37 Buil by Puteaux and lighter than the M-34, but with similar performance)
3.7 cm PAK 153 (h) (ex-dutch 37mm Rheinmetall, buyed to Germany)
3.7 cm PAK 158 (r) (ex russian 37 mm M 30, similar to the PAK 36, buyed to Germany)
3.7 cm PAK 162 (i) (ex-italian Canone contracarro da 37/45, PAK 36 buyed to Germany)
3.7 cm PAK 37 (t) (ex-czech M-37, issued to German troops after seizure of Czechoslovaquia)
3.7 cm PAK 156(j) (ex-jugoslavian M-37 Skoda)
3.7 cm PAK 36 (p) (ex-polish M-36, built by Bofors, and used also by the Finns and the British as Ordnance QF, 37 mm Mk I)
3.7 cm PAK 157 (d) (ex-danish M-34 Bofors, same gun as above)
3.7 cm PAK 164 (d) (ex-danish M-35 Madsen)
4.0 cm PAK 154 (b) (ex british 2 pounders used by the Belgian Army)
4.0 cm PAK 192 (e) (ex-british QF2 on carriage 2pr)
4.5 cm PAK 184 (r) (ex-russian M-30, a scaled up version of the PAK 36 )
4.5 cm PAK 184/1 (r) (ex-russian M-32, development of the M-30)
4.5 cm PAK 184/6 (r) (ex-russian M-36, the M-38 tank gun on makeshift carriage)
4.7 cm PAK 36 (t) (ex-czech M-36, very appreciated by German troops)
4.7 cm PAK 177 (i) (ex-italian M-35 Böhler)
4.7 cm PAK 179 (j) (ex jugoslavian M-36 Skoda)
4.7 cm PAK 181 (f) (ex french M-37,a very effective AT gun, also known as SA 37 APX)
4.7 cm PAK 183(f) (ex french M-39, development of the M-37)
4.7 cm PAK 185 (b) (ex-belgian Con de 47 antichars SA-FRC)
4.7 cm PAK 188 (h) (ex dutch Kanon van 47)
4.7 cm PAK 196 (r) (ex-russian 47 mm PTP Böhler)
5.7 cm PAK 208 (ex-russian M-41/ZIS-2)
7.5 cm PAK 97/38 (french 7.5 cm in PAK 38 carriage, used only until arrival of the PAK 40)
7.5 cm PAK 97/40 (french 7.5 cm in PAK 40 carriage)
7.62 cm PAK 36 (r) (ex-russian M-36)
7.62 cm PAK 39 (r) (ex-russian M-39 also called FeldKanone 297)
7.62 cm PAK 54 (r) (ex-russian, russian designation unknown)